Thread delivery method and apparatus

ABSTRACT

A method and an apparatus for regulating the rotational speed of a storage drum of a thread storage device in a thread processing machine. The storage drum is driven by a winding drive comprising an electromotor and the thread is tangentially wound onto the storage drum to form a thread supply. The electromotor is switched off by a movable and electrically controllable switch device when a maximum thread supply is obtained and switched on by means of a scanning member scanning the actual quantity of thread when a minimum thread supply is obtained. When the thread supply slightly exceeds or falls below a given quantity, the scanning member switches the electromotor on and off with the aid of the switch device with such frequency that the rotational speed of the storage drum adapts itself to the speed of the unwinding thread and the thread supply on the storage drum is kept practically constant.

United States Patent J acobsson [4 1 Mar. 12, 1974 THREAD DELIVERY METHOD AND APPARATUS Primary Examiner-Stanley N. Gilreath Attorney, Agent, or Firm-Woodhams, Blanchard &

Flynn [5 7 ABSTRACT A method and an apparatus for regulating the rota tional speed of a storage drum of a thread storage device in a thread processing machine. The storage drum is driven by a winding drive comprising an electrometor and the thread is tangentially wound onto the storage drum to form a thread supply. The electromotor is switched off by a movable and electrically controllable switch device when a maximum thread supply is obtained and switched on by means of a scanning member scanning the actual quantity of thread when a minimum thread supply is obtained. When the thread supply slightly exceeds or falls below a given quantity, the scanning member switches the electromotor on and off with the aid of the switch device with such frequency that the rotational speed of the storage drum adapts itself to the speed of the unwinding thread and the thread supply on the storage drum is kept practically constant.

11 Claims, 3 Drawing Figures Pmmznnm an 3796; 385

SHEET 2 0F 3 Fig. 2

1 THREAD DELIVERY METHOD AND APPARATUS The invention relates to a method of regulating the rotational speed of the storage drum of a thread delivery device for a thread processing machine,wherein the storage drum is driven by an electromotor and the thread is tangentially wound onto the storage drum thereby forming a thread supply, and wherein the electromotor is switched off by a movable and electrically controllable device when a maximum thread supply is reached and switched on by a scanning member which scans the actual quantity supply when a minimum supply is arrived at.

The term thread processing machines refers generally to machines to which one or more threads are simultaneously fed for subsequent treatment. Textile machines such as knitting machines may be cited as an example.

A thread storage device is intended for storing a specific minimum quantity of thread (or yarn) running off a bobbin on its storage drum and delivering it under as constant a tension as possible to the further processing machine. in this connection the thread supply on the drum is continually moved in an axial direction and new thread wound on. The size of the thread supply on the storage drum is therefore limited in both upward and downward directions. On the one hand, a minimum quantity of thread must be ensured to enable troublefree operation of the storage device so that, in the event of a thread breakage located during thread delivery to the storage device, the thread processing machine which is usually brought to a standstill only slowly on account of its great size is still supplied with an adequate quantity of thread. On the other hand, however, a maximum quantity should not be exceeded in order not to complicate the winding-off operation.

There is already a known thread feeder for a thread processing machine in which the storage drum is driven by a two-phase asynchronous motor. A thyristor is provided in each of the two feed-in wires of the motor. The two thyristors are connected to a control circuit whereby their switch position may be controlled. The control circuit comprises a potentiometer at which the switch time of the thyristors may be set during each period of alternating voltage. The rotational speed of the storage drum may be determined in this way. Connected to this control circuit is a photoelectric cell which acts as a scanning member for monitoring the quantity of thread on the storage drum. The drive motor for the storage drum is stopped when a pennitted maximum quantity of thread is exceeded. When the storage drum is stationary, the maximum permitted quantity of yarn is reduced during constant yarn withdrawal to a permitted minimum thread supply and the storage drum is then returned to the set rotational speed by the photoelectric cell control. During operation of this known apparatus a change in movement of the drum from complete stoppage to the rotational movement at a set speed is effected in a cyclic manner. This apparatus is subject to the following movement during operation: thread is constantly withdrawn from the stationary storage drum thereby constantly reducing the thread supply on said drum. When the minimum thread supply is arrived at, the switch is closed and the electromotor switched-on. The storage drum is thereby set into rotation and winds such a quantity of thread from the bobbin onto the storage drum until the maximum thread supply is restored. At this point of time the electromotor is switched off and the storage drum stopped again. This known method or the apparatus for carrying out said method has a number of disadvantages. The thread which is axially wound off the storage drum is variably wound depending on the position of movement, i.e., a predetermined winding speed or stoppage, of the storage drum. The greater the winding, the greater the difference in the speeds at which the thread is wound on or withdrawn. In the case of storage devices in which the storage drum is subjected to a rotational movement to wind on the thread, as applies to the described known apparatus, there is formed a socalled balloon of thread during the time when the thread is being wound on. This phenomenon is due to the fact that the piece of thread being axially withdrawn from the storage drum also rotates about the axis of the storage drum and is therefore forced outwards in the form of a balloon by centrifugal forces. As the thread balloon is not constant during the described movement, but disintegrates once during each control cycle, periodic fluctuations occur in the tension of the unwinding thread. These fluctuations are caused by variable air drag and centrifugal forces acting on the thread.

Accordingly the problem underlying this invention is to provide a method of regulating the rotational speed of the storage drum of a thread delivery device for a thread processing machine, wherein the tension acting on the thread being withdrawn and the unwinding of the thread are kept as constant as possible.

This problem is solved in accordance with the invention in that, if the thread supply slightly exceeds or falls below a given value, the scanning member with the aid of the switch device switches off or on the electromotor with such frequency that the rotational speed of the drum is adapted to correspond to the speed of the unwinding thread and the quantity of thread on the storage drum is kept practically constant.

The invention is based on the previously applied principle of allowing the thread on the storage drum to fluctuate between clearly distinguishable minimum and maximum values. The electrically controllable switch device which is not subjected to inertia may be switched on and off at high frequency. Owing to the low power required by the scanning member the latter can be correspondingly sensitive in design. During operation of this arrangement a constant position is established in which a given nominal thread supply is kept practically constant on the storage drum. [n the case of the storage devices having rotary storage drums the speed of the storage drum is automatically adapted to the speed of the unwinding thread, thereby avoiding any twisting of this thread. The danger of knots forming is practically eliminated as the thread is constantly in motion. Nor is a balloon of thread formed because the unwinding thread no longer rotates intermittently on a conical face lying symmetrically to the axis of rotation of the storage drum, but is stationary practically in a direction perpendicular to its longitudinal extension. The troublesome influences associated with known methods are therefore totally eliminated. Any braking devices located on the drum are subjected to constant centrifugal forces owing to the constant rotational speed of the drum and accordingly exert a constant braking force on the unwinding thread. However, the invention is applicable not only to storage devices having moving storage drums. A constant operation also occurs with arrangements having a stationary storage drum, whereby the tension of the unwinding thread is kept practically constant because on account of the constant thread supply the distance between the withdrawal loop and the thread supply gives rise to the formation of a constant balloon of thread. Another advantage which can be achieved with the arrangement according to the invention is that the constant thread supply on the storage drum can be selected so as to be approximately equal to the maximum required quantity of thread. This is approximately the quantity which could be the set minimum quantity in the described known arrangement, thereby also simplifying the winding operation. In contrast to known arrangements of this type, the described arrangement provides the opportunity to use an asynchronous motor, particularly a hysteris synchronous motor which may be extremely well controlled in pulse width regulation.

Other features and advantages of the invention are shown in the following description of a practical embodiment with the aid of the drawings.

FIG. 1 is a side view of a thread storage device,

FIG. 2 shows a partial view of the thread storage device in which the scanning means and the switch device can be clearly seen, and

FIG. 3 shows an embodiment of an associated circuit diagram according to the invention for controlling the electromotor.

In FIG. 1 a bobbin 2 mounted on a vertical spindle 3 is supported on a carrier arm 1 which is connected to a frame (not shown) of a textile machine, for example a knitting, weaving or winding machine. A thread F is wound upwards off this bobbin and fed tangentially through or via various thread guide elements 4, 5 and 6 to a storage drum which is generally designated by reference numeral 7. A thread brake of known construction, for example a disc brake, is fitted in the path of the thread F between the bobbin 2 and the storage drum 7.

The storage drum 7 is rotatably mounted in the lower side of the carrier arm 1 and can be rotatably driven for winding purposes by a motor (which is not shown in this drawing). In the illustrated embodiment the drum 7 comprises a cylindrical cage of rods acting as an actual winding member. The thread is woundonto the outer walls of the rods forming the cage. Inside the drum a spoke wheel which is not shown in detail but can be seen in FIG. 2 is mounted at an inclined angle relative to the longitudinal axis of the storage drum 7 and spring-loaded in the direction of inclination. Its spoke-like arms extend through the rods of the storage drum and their free ends are connected by a thrust ring 9 which bears closely against the outer face of the rods 70 in the area of the storage drum 7 in which the thread F is delivered. The ring 9 can be pivoted in the direction of the double arrow P shown in FIG. 2. The ring 9 functions as a portion of a mechanical scanning member for sensing changes in the size of the yarn reserve 17.

A pin 10 which is arranged in the centre of the ring and is perpendicular to the plane of the ring is connected to the ring 9 by the spokes of the spoke wheel. A switch which is generally designated by reference numeral 11 is located in the area of movement of this pin 10. Located in the housing of this switch are two contacts 13 which are connected to electrical leads 12 and can be short-circuited by a spring-loaded ball 14. A mechanically operable contact pin 15 by means of which the ball 14 can be lifted clear of the contacts 13 extends through the wall of the housing. The contact pin 15 is supported on the pin 10 by a sliding member 16 attached to its end.

The thread F coming off the bobbin is delivered to the storage drum 7 at point A (FIG. 2). The thread is moved downwards with the inclined thrust ring 9 which causes the thread to be wound onto the already existing multi-layered ball of thread 17. The ring 9 is tilted by the increasing supply of thread at the delivery point on the ball of thread. The pin 10 connected to the ring causes the ball 14 in the switch 11 to be lifted clear from the contacts 13 with the aid the contact pin 15. As will be described in more detail, the electrometer 18 is thereby disconnected from the voltage supply. It should also be noted that the ball of thread which is loaded by the ring 9 is subjected to a constant axial movement.

The apparatus shown in FIG. 3 for controlling the electromotor 18 represents a three-phase system having leads R, S and T. An electrically controllable switch element 19, for example a thyristor is located in each lead in the phase system. The control wire 20 of each of the switched elements 19 is connected to the anode of the same switch element 19 by a resistor 21, the already described switch 11 and a diode 22. A diode 23 is connected in parallel with each of the switch elements 19. The resistors 21 serve to protect the switch elements 19 from overloading.

When the switch 11 is opened the control electrodes of the switch elements 19 are disconnected from the voltage supply whereupon these switch elements 19 represent a very high resistance. The motor 18 is in the switch-off position. By closing the switch 1 l the control leads 20 receive voltage via the diodes 22 and the resistors 21. The switch elements 19 are thereby moved into the open position, which means that the motor 18 is switched-on. Since the conventional electrically controllable switch elements are usually conductive in only one direction, there are provided the diodes 23 connected in parallel which take over conduction of current in the other direction. A thyristor 19 combines with the diodes 23 of the other two thyristors and the motor winding to form a circuit which is closed by the voltage supply. The current feed is therefore controlled by the thyristors 19 whereas the current is freely discharged via the diodes 23. The motor 18 is therefore supplied with complete phases for alternating current.

During operation of the storage device a constant condition is established in which the speed with which the thread is wound on is adapted to correspond to the speed with which the thread is unwound. When the wind-on speed is is only slightly less than the wind-off speed, the switch 11 causes the pulses of voltage with which the motor 18 is supplied to be lengthened; whereupon the wind-on speed immediately adapts itself again to the wind-off speed. The result is that in practice there are fluctuations in the quantity of thread on the storage drum, which fluctuation lie below 5 percent (a maximum discrepancy in an average thread supply of above 5 percent and a maximum discrepancy of below 5 percent) of an average thread supply. An easily obtainable range of fluctuation is i: 3 percent or even less. In a practical embodiment discrepancies of approxiamtely i 1.5 percent in the quantity of thread on the storage drum were observed where the wind-off speed of the thread varied between 100 and 235m/min.

The invention is not limited to the described embodiment. All electrically controllable and movable control devices, such as transistors and thyratrons, are particularly suitable for use as the switch element. The illustrated switch 11 can also be designed in any desired form. It only needs to be noted that if it is mechanical in design, it is easy to operate. The mechanical construction can be replaced for example by an electronic circuit which is controlled by the scanning member. The scanning member itself can be, for example, in the form of a photoelectric scanner. All pressure-sensitive elements are suitable as scanning members and permit the pressure produced by a mechanical scanning member to be converted into an electrical signal which either controls the switch 11 or forms the actual switch. A two-phase system can be correspondingly designed to control the electromotor. When a direct-current motor is used it is sufficient to provide a switch or control device in only one of the power lines.

What I claim is:

l. A thread delivery device for a thread processing machine, comprising in combination:

a rotatable storage drum on which a thread can be wound tangentially to form a thread supply and from which said thread is removable;

an electromotor for driving said storage drum to wind thread thereon and electrical power source means for said electromotor;

scanning means for scanning the quantity of thread actually on the storage drum and responsive to slight variation thereof for changing state;

means, including an electronic switch element, interposed between said power source means and said electromotor and responsive to said scanning device change of state for adapting the rotation speed of the storage drum to the speed of the unwinding thread by switching the electromotor on and off with such frequency as to maintain the quantity of thread on said storage drum practically constant;

whereby to avoid repetitive stop-start cycling of storage drum rotation and consequent changes in the tension of thread removed from said storage drum.

2. Apparatus claimed in claim 1 in which;

said scanning means includes a switch, said electromotor is a multiphase motor, said power source means comprises a plurality of phase lines, said interposed means comprises a plurality of electronic switch elements each consisting of a thyristor connecting each phase of said electromotor to corresponding phase line,

said thyristors each having a gate for initiating conduction therethrough, plural diodes connecting said corresponding phase lines individually to one side of said switch and corresponding resistances connecting said gates to the other side of said switch, shunting diodes connecting in reverse orientation across each of said thyristors, each thyristor being provided a conduction path from its corresponding phase line therethrough and through said motor and thence back to said source through the shunting diodes associated with other phases of said motor.

3. Apparatus as claimed in claim 1, in which;

said scanning means includes a thrust ring for contacting said thread supply, and means defining a switch in contact there-with and actuable thereby at high frequency for switching a relatively low gate current flow to said electronic switch. 4. Apparatus as claimed in claim 3, in which said electromotor is a three phase motor, said source means comprises three phase lines, and said interposed means comprises three thyristors connected in each respective phase line of said power source means and said electromotor for controlling electromotor current flow.

5. Apparatus as claimed in claim 1, in which said electromotor is a polyphase motor and said interposed means comprises plural electrically controllable electronic switch elements each located in a different power supply line of said polyphase motor.

6. Apparatus as claimed in claim 5 in which each of the switch elements is connected in parallel to a diode polarized reversely of said switch element so that it permits the flow of current in the closing direction of the switch element from an open one of the remaining switch elements.

7. Apparatus as claimed in claim 5, in which said switching elements comprise thyristors, the scanning member comprises a mechanical switch and including control leads connecting the gates of said thyristors to the anodes thereof through said switch.

8. Apparatus as claimed in claim 7 including a resitor and a diode in series in each of the control leads, said diodes being oriented for actuating their corresponding thyristor gates with the phase applied to the anode thereof when said switch is conductive.

9. Apparatus as claimed in claim 1 characterized in that the scanning means comprises a switch capable of high frequency actuation, said switch having contacts and a ball having a conductive surface engageable with said contacts for electrically connecting same.

10. Apparatus as claimed in claim 1 in which said scanning means includes a thread quantity sensing member and switch responsive to variation in thread quantity in said thread supply less than :5 percent.

11. A method of regulating the rotational speed of the storage drum of a thread delivery device for a thread processing machine, wherein the storage drum is driveable by an electromotor, comprising the steps of:

winding thread tangentially onto the storage drum as same is driven to form a thread supply while allowing thread to be removed from said storage drum;

scanning the actual quantity of thread in the thread supply on said storage drum;

changing the state of a scanning device when the thread supply deviates from a given quantity by a maximum of :5 percent.

maintaining the rotational speed of the storage drum in close correspondence with the speed of the unwinding thread by electrically switching on and off said electromotor in correspondence to the frequency of said change of state of said scanning device;

whereby the thread supply onthe storage drum is kept substantially constant. 

1. A thread delivery device for a thread processing machine, comprising in combination: a rotatable storage drum on which a thread can be wound tangentially to form a thread supply and from which said thread is removable; an electromotor for driving said storage drum to wind thread thereon and electrical power source means for said electromotor; scanning means for scanning the quantity of thread actually on the storage drum and responsive to slight variation thereof for changing state; means, including an electronic switch element, interposed between said power source means and said electromotor and responsive to said scanning device change of state for adapting the rotation speed of the storage drum to the speed of the unwinding thread by switching the electromotor on and off with such frequency as to maintain the quantity of thread on said storage drum practically constant; whereby to avoid repetitive stop-start cycling of storage drum rotation and consequent changes in the tension of thread removed from said storage drum.
 2. Apparatus claimed in claim 1 in which; said scanning means includes a switch, said electromotor is a multiphase motor, said power source means comprises a plurality of phase lines, said interposed means comprises a plurality of electronic switch elements each consisting of a thyristor connecting each phase of said electromotor to corresponding phase line, said thyristors each having a gate for initiating conduction therethrough, plural diodes connecting said corresponding phase lines individually to one side of said switch and corresponding resistances connecting said gates to the other side of said switch, shunting diodes connecting in reverse orientation across each of said thyristors, each thyristor being provided a conduction path from its corresponding phase line therethrough and through said motor and thence back to said source through the shunting diodes associated with other phases of said motor.
 3. Apparatus as claimed in claim 1, in which; said scanning means includes a thrust ring for contacting said thread supply, and means defining a switch in contact there-with and actuable thereby at high frequency for switching a relatively low gate current flow to said electronic switch.
 4. Apparatus as claimed in claim 3, in which said electromotor is a three phase motor, said source means comprises three phase lines, and said interposed means comprises three thyristors connected in each respective phase line of said power source means and said electromotor for controlling electromotor current flow.
 5. Apparatus as claimed in claim 1, in which said electromotor is a polyphase motor and said interposed means comprises plural electrically controllable electronic switch elements each located in a different power supply line of said polyphase motor.
 6. Apparatus as claimed in claim 5 in which each of the switch elements is connected in parallel to a diode polarized reversely of said switch element so that it permits the flow of current in the closing direction of the switch element from an open one of the remaining switch elements.
 7. Apparatus as claimed in claim 5, in which said switching elements comprise thyristors, the scanning member comprises a mechanical switch and including control leads connecting the gates of said thyristors to the anodes thereof through said switch.
 8. Apparatus as claimed in claim 7 including a resitor and a diode in series in each oF the control leads, said diodes being oriented for actuating their corresponding thyristor gates with the phase applied to the anode thereof when said switch is conductive.
 9. Apparatus as claimed in claim 1 characterized in that the scanning means comprises a switch capable of high frequency actuation, said switch having contacts and a ball having a conductive surface engageable with said contacts for electrically connecting same.
 10. Apparatus as claimed in claim 1 in which said scanning means includes a thread quantity sensing member and switch responsive to variation in thread quantity in said thread supply less than + or - 5 percent.
 11. A method of regulating the rotational speed of the storage drum of a thread delivery device for a thread processing machine, wherein the storage drum is driveable by an electromotor, comprising the steps of: winding thread tangentially onto the storage drum as same is driven to form a thread supply while allowing thread to be removed from said storage drum; scanning the actual quantity of thread in the thread supply on said storage drum; changing the state of a scanning device when the thread supply deviates from a given quantity by a maximum of + or - 5 percent. maintaining the rotational speed of the storage drum in close correspondence with the speed of the unwinding thread by electrically switching on and off said electromotor in correspondence to the frequency of said change of state of said scanning device; whereby the thread supply on the storage drum is kept substantially constant. 